Characteristics: Tulsi is a small fragrant herb often with purple-green leaves that is found growing wild and is cultivated throughout south East Asia and India (Kuhn and Winston, 2000). It is widely distributed in India and found growing from the sea level up to 1800m in altitude high in the Himalayas (Mondal et al., 2011). There are three varieties of this plant: Rama tulsi (green leaves), Vana tulsi (green leaves), and Krishna tulsi (red-purple leaves) (Kuhn and Winston, 2000).

History: Tulsi is sacred to the Hindu God Vishnu and in India it is often used in morning prayer for personal health, spiritual and family well-being (Winston, 2007). String made from the plants stem are used in meditation as it is thought to give clarity and protection. Tulsi is a rasayana herb in Ayurveda, otherwise known as a rejuvenator, and is thought to nourish a person towards health and long life. Daily use of the herb is said to be associated with balancing the chakras or energy centres of the body. In the Puranas, everything associated with the herb is holy, i.e. the water given to it, the soil it grows in, and all its botanical parts (leaves, stem, flower, and so on). In Indian folk medicine, the leaves are brewed as a tea and this is used as an expectorant to help those with excessive bronchial mucus and bronchitis. It has a long history of medicinal use and is mentioned in the Charaka Samhita, an ancient Ayurvedic text (Vats et al., 2004). Traditional use of tulsi is for bronchitis, bronchial asthma, dysentery, dyspepsia, skin diseases, and chronic fever.

Current applications: Maria Groves describes tulsi as a greater protector (Groves, 2016). She mentions tulsi improve health of the immune system to fight infections, strengthens digestion, decreases inflammation, and relieves anxiety. David Winston uses holy basil to enhance cerebral circulation and memory (Winston, 2007). Tulsi relieves mental fog and can be combined with bacopa, rosemary, and ginkgo for this and other cognitive problems, such as, ADD, ADHD, and head trauma. Combined with reishi and blueberry extract tulsi may be effective in reducing allergies. David Frawley writes tulsi is a specific for depression alongside calamus (Frawley, 2000).

Science: Tulsi has been well studied using various experimental models and the data generally support its medicinal value. Tulsi has anti-inflammatory, anti-oxidant, analgesic, and anti-tumour effects (Godhwani et al., 1987; Kelm et al., 2000; Magesh et al., 2009). Using in vivo models, it also displayed nootropic effects (neuroprotective) suggesting it may have a role in treating Alzheimer’s or dementia (Joshi et al., 2006). Another study found it had cardioprotective properties, therefore suggesting it may have a role in treating heart problems (Sharma et al., 2001). An additional study found it reduced neuropathy in rats possibly due to anti-oxidant activity (Muthuraman et al., 2008).

There are a number of double blind placebo controlled studies of tulsi in humans, one study examined tulsi’s immunological effects in healthy individuals to find it increased levels of both NK and T regulatory cells after 4 weeks (Mondal et al., 2011). This study supports the immunomodulatory role of tulsi in herbal medicine, however, it also emphasises that its role on the immune system is likely complex. Tulsi does not simply repress inflammation, but likely modulates the immune system in complex ways. We need more human studies of infectious and autoimmune diseases to decipher how tulsi behaves in these types of disease. Another human study found significant reduction in stress with tulsi treatment (Saxena et al., 2011), similar to other adaptogens. An additional double blind placebo controlled study found that tulsi treatment appeared to enhance human cognitive powers to support its nootropic classification (Sampath et al., 2015).

Safety: High, however, avoid during pregnancy and it may interfere with trying to conceive.

Anti-inflammatory/ anti-oxidant: Extraction of tulsi compounds from leaves and stems resulted in the extraction of; cirsilineol, cirsimaritin, isothymusin, isothymonin, apigenin, rosmarinic acid, and eugenol (Kelm et al., 2000). Various experiments were performed ex vivo. Eugenol was found to have potent anti-oxidant effects, while other compounds were found to inhibit both cyclooxygenase-1 and cyclooxygenase-2 inflammatory pathways.

Nootropic properties: A study using in vivo experimental models found tulsi extract reduced the amnesic effect of administration of scopolamine and diazepam (Joshi et al., 2006). The authors concluded this suggests it may have a role in the treatment of Alzheimer’s or dementia.

Cardioprotective: One study found that tulsi extract exhibited a cardioprotective effect using in vivo experimental models (Sharma et al., 2001).

Anti-tumour: A study found anti-tumour activity in ex vivo and in vivo models of lung cancer (Magesh et al., 2009). Tulsi extract was found to induce apoptosis in A549 cells via a mitochondria caspase dependent pathway.

Neuroprotective: One study detected an ameliorative effect of tulsi on peripheral neuropathy in rats, the authors hypothesised anti-oxidant and calcium attenuating effects may be related to this action (Muthuraman et al., 2008).

Stress: A study (n = 150, double blind placebo controlled) found taking three 400mg capsules of tulsi extract per day over six weeks led to significant reductions in forgetfulness, exhaustion, sleep problems, and stress (Saxena et al., 2011).

Nootropic activity: One study (n=44, double blind placebo controlled) found individuals who took 300 milligram capsules of ethanolic leaf extracts of Ocimum sanctum per day, over 30 days, had a significant cognitive boosting effect in healthy individuals compared to the control group (Sampath et al., 2015).